Refrigerator appliances generally include a compressor. During operation of the refrigerator appliance, the compressor operates to provide compressed refrigerant. Such compressed refrigerant is utilized to cool a compartment of the appliance and food items stored therein.
Certain refrigerator appliances include a reciprocating compressor that compresses refrigerant by sliding a piston within a chamber. Reciprocating compressors can include a piston mounted to a crankshaft. As the crankshaft turns, the piston slides within the chamber in order to compress refrigerant. However, the large number of moving parts associated with the piston and crankshaft can generate large friction forces. Such friction can result in poor efficiency and negatively affect performance of the refrigerator appliance.
Recently, linear compressors have been used to compress refrigerant in refrigerator appliances. Linear compressors can include a piston and a driving coil. The driving coil generates a force that slides the piston backward and forwards within a chamber to compress refrigerant. However, linear compressors can require active control for every piston stroke in order to stop motion of the piston at either end of displacement. Such control can be complex and expensive.
In certain linear compressors, the piston is mounted to a spring that urges the piston towards a default position. In such a configuration, the piston oscillates from the default position with an amplitude that depends on the magnitude and frequency of force applied to the piston by the driving coil. By adjusting the strength of the driving coil's force and the frequency of application of such force, the piston can slide within the chamber at a resonant frequency in which the amplitude of the piston's displacement is maximized for the force applied to the piston. However, the spring can be inefficient at storing energy during motion of the piston and negatively affect compressor performance. In addition, the total spring force applied to the piston during a compression stroke can be non-linear. Such non-linearity can decrease the efficiency of the linear compressor and negatively affect compressor performance.
Accordingly, a linear compressor with features for operating at a resonant condition would be useful. In particular, a linear compressor with features for applying a linear total spring force to a piston of the linear compressor would be useful.